Like a muffin top, only lower, and specifically in the rear. Caused by insanely too-tight shorts or pants that squeeze one's butt cheeks out like it's butt cleavage.
plumbers crack muffin top
It wasn't just a plumber's crack, there was serious button top on display.
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.
We have a Zoom meeting in a few minutes and I’ll probably go pajama casual.